1. Field of the Invention
The present invention relates, in general, to polishing slurries comprising multi-metal oxide nanoscale powders and methods for their manufacture and use.
2. Relevant Background
Polishing of surfaces is employed in chip manufacturing, telecom component manufacturing, data storage product manufacturing, and optical component manufacturing. Polishing and abrasive cleaning of surfaces is also employed in numerous other industrial and consumer products. This technology currently uses sub-micron particles of single metal oxides such as alumina, silica, ceria, zirconia, and titania. However, with increasingly complex surfaces, both hard and soft, novel polishing slurries are desired.
Nanopowders in particular and sub-micron powders in general are a novel family of materials whose distinguishing feature is that their domain size is so small that size confinement effects become a significant determinant of the material's performance. Such confinement effects can, therefore, lead to a wide range of commercially important properties. Nanopowders, therefore, are an extraordinary opportunity for design, development and commercialization of a wide range of devices and products for various applications. Furthermore, since they represent a whole new family of material precursors where conventional coarse-grain physiochemical mechanisms are not applicable, these materials offer unique combination of properties that can enable novel and multifunctional products of unmatched performance. A commonly-owned patent Bickmore et al. in U.S. Pat. No. 5,984,997, which along with the references contained therein are hereby incorporated by reference in full, teach some applications of sub-micron and nanoscale powders. Co-pending application Ser. No. 09/638,977, which along with the references contained therein are hereby incorporated by reference in full, teaches methods for producing very high purity nanoscale materials and their applications.
In U.S. Pat. No. 6,068,787, which along with its references is herewith incorporated herein in full, Grumbine et al. (Cabot Corp.) report a chemical mechanical polishing precursor comprising at least one catalyst having multiple oxidation states, and at least one stabilizer, the composition being useful when admixed with an oxidizing agent prior to use to remove metal layers from a substrate. This method is used to facilitate the formation of oxides from various metal layers. This approach does not address the significant difference in the hardness of soft materials and the powders used in CMP slurries.
In U.S. Pat. No. 6,063,306, which along with its references is herewith incorporated herein in full, Kaufman et al. (Cabot Corp) report using alumina, titania, ceria, silica, and zirconia to prepare CMP slurries for polishing metals and nitrides. They report a good metal selectivity. However, the other issues such as dishing, pitting etc. are not addressed in this report.
In U.S. Pat. No. 6,045,435, which along with its references is herewith incorporated herein in full, Bajaj et al. (Motorola) report a low selectivity CMP process to address the problem of dishing. They discuss in significant detail the problems with dishing when conventional abrasives are used. Their approach is to trade-off selectivity for the uniformity and quality of the polish.
In most applications, polishing slurries need to satisfy a complex combination of functional and processing requirements. Single metal oxide sub-micron powders in general, and nanoscale powders in particular fail to meet all these requirements. This invention is directed to address this limitation.
Definitions
Fine powders, as the term used herein, are powders that simultaneously satisfy the following:    1. particles with mean size less than 100 microns, preferably less than 10 microns, and    2. particles with aspect ratio between 1 and 1,000,000.
Submicron powders, as the term used herein, are fine powders that simultaneously satisfy the following:    1. particles with mean size less than 1 micron, and    2. particles with aspect ratio between 1 and 1,000,000.
Nanopowders (or nanosize powders or nanoscale powders or nanoparticles), as the term used herein, are fine powders that simultaneously satisfy the following:    1. particles with mean size less than 250 nanometers, preferably less than 100 nanometers, and    2. particles with aspect ratio between 1 and 1,000,000.
Single metal oxide (or simple oxide), as the term is used herein, are powders whose composition comprises of a single metal and oxygen.
Multi-metal oxide (or complex oxide), as the term is used herein, are powders whose composition comprises of at least two metals and oxygen.
Pure powders, as the term used herein, are powders that have composition purity of at least 99.9%, preferably 99.99% by metal basis.
Powder, as the term is used herein encompasses hollow, dense, porous, semi-porous, coated, uncoated, layered, laminated, simple, complex, dendritic, inorganic, organic, elemental, non-elemental, composite, doped, undoped, spherical, non-spherical, surface functionalized, surface non-functionalized, stoichiometric, and non-stoichiometric form or substance.